Rename CallWithContinuation trait to Then

New name is shorter and better reflects the intent of the trait.

src/main.rs

@@ -110,11 +110,23 @@ fn main() {
 	}
 }
 
-trait WithContinuation<T> {
+// Represents a type characterised by a parameter T (either the type itself, or
+// a type inside it, as in case of Option<T>), on which we can call a procedure
+// that doesn't return anything.
+//
+// This is similar to `and_then` method that Option and Result expose, the only
+// difference being in that this is only useful for procedures that perform
+// side effects, as we don't return either the original value, or a new value
+// being a result of the procedure.
+//
+// The function name this trait exposes is similar to `then` method found on
+// bool type, as the original intent was to call it if the value is Some, and
+// do nothing if it's None.
+trait Then<T> {
 	fn then<F>(&self, f: F) where F: FnOnce(&T);
 }
 
-impl<T> WithContinuation<T> for std::option::Option<T> {
+impl<T> Then<T> for std::option::Option<T> {
 	fn then<F>(&self, f: F) where F: FnOnce(&T) {
 		match self {
 			None => {},